Bypass mechanism for a hydraulic drive apparatus
A bypass mechanism for a hydraulic apparatus is provided, where a rotatable hydraulic component such as a motor cylinder block is disposed on a running surface and in fluid communication with a closed hydraulic circuit. The hydraulic component is drivingly engaged to a shaft, such as a motor shaft. An arm or similar mechanism is engaged to the shaft to move it from a standard operating position to a second position where the shaft engages the hydraulic component to lift the component off its running surface, thereby placing the hydraulic apparatus into bypass by opening the closed hydraulic circuit to a sump.
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This application claims the priority of U.S. Provisional Application Ser. No. 60/657,762, filed on Mar. 1, 2005 and U.S. Provisional Application Ser. No. 60/664,803 filed Mar. 24, 2005. Both of these prior applications are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTIONThis invention relates to a hydrostatic transaxle for use in vehicles, industrial applications or other applications.
SUMMARY OF THE INVENTIONA hydrostatic transaxle is disclosed herein. The various features and benefits of this transaxle provide a more compact and less expensive design than prior art models. Among the features disclosed herein are an improved internal brake mechanism, an improved gear arrangement and support structure for the gear train, an improved bypass mechanism, an improved pump swash plate design and an improved filter design. It will be understood that each of these improved features can be used in combination with other features disclosed herein or on their own.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and is indicative of the various ways in which the principles of the invention may be employed.
Various bearings, spacers, seals and similar items are depicted in the figures but not described in detail as the operation and assembly of such an integrated hydrostatic transaxle will be known to those of skill in the art. In addition, there are different embodiments described herein; to the extent there are identical or substantially identical structures used in these embodiments, identical numerals are used. Where structures are described between embodiments that vary from previous embodiments a prefix may be added to a previously described number. For example, item numbers 3, 103 and 203 all describe center sections of similar design.
In prior designs, such as in U.S. Pat. No. 6,253,637, intermediate shafts are used to mount various gears in the gear train. In the present invention, on the other hand, the gear train is mounted on motor output shaft 24 and on or generally coaxial with axles 35a and 35b. This arrangement can be seen most clearly in
Output gear 27 is splined on motor shaft 24 by means of splines 24a, as shown most clearly in
As can be seen in
Center section 3 of the present invention may be of the design shown in
An alternative design of such a spacer unit is shown in
When used in an application such as a vehicle, a closed circuit such as hydraulic porting 25 in center section 3 preferably includes a means for placing the hydraulic circuit into communication with sump 11 to make the vehicle easier to move when prime mover 14 is not engaged. A known bypass system includes the use of a puck to lift the motor block off the motor running surface of a center section, such as is shown in U.S. Pat. No. 5,314,387. When the block is lifted off the motor running surface, the hydraulic fluid is discharged to the sump from the closed circuit through the kidney ports on the motor running surface. Another known bypass mechanism lifts the two check balls off their respective check valve seats, such as is disclosed in U.S. Pat. No. 6,253,637.
The present invention provides an improved bypass method; in general terms, the motor shaft is movable along its axis in order to engage and lift the motor cylinder block off its running surface on the center section. Different embodiments of this design, including various means of both supporting the motor shaft and placing the unit into bypass in accordance with this invention are disclosed herein. Where appropriate, identical numerals in the figures represent identical or substantially identical structure.
First, with regard to the transaxle 210 embodiment disclosed in
A bypass rod 248 has a first end that extends into an opening formed in housing 202 and a second end on which bypass arm 249 is mounted. Shoulder 252 on motor shaft 224 is positioned in cam opening 250 formed on rod 248. As bypass arm 249 is activated and the force of bias spring 257 is overcome, bypass rod 248 rotates from the position shown in
A slightly modified embodiment of a bypass mechanism is depicted in
A return force is provided by helical compression spring 78 which is mounted on housing 1 and engaged to washer 77 adjacent to the end of motor shaft 24. A return force is also provided by the force of motor piston springs 43 in motor pistons 44 as pistons 44 engage fixed swash plate or thrust bearing 21. Finally, a spring similar to spring 257 shown in
A further embodiment of a bypass mechanism is depicted in
Cradle mounted swash plates are known in the art and are disclosed, for example, in U.S. Pat. No. 5,201,692. There are certain disadvantages to cradle mounted swash plates, such as the change in control moments over the life of the cradle bearing. As control moments increase, it is more difficult to operate the swash plate, which is a disadvantage for foot controlled units.
Another design known in the art comprises a pair of trunnions located on opposite sides of the swash plate. Such designs, however, require the trunnions to extend out and be supported at both sides of the swash plate. In a vertically split housing such as the present design, this would require the trunnions to be supported in both housings 1 and 2. Prior art trunnion designs are also disadvantageous in that their control moments may be too low.
In one feature of the present design, swash plate 4 comprises a main body portion 40 in which the thrust bearing 19 is mounted for engaging the pump cylinder pistons 20, as shown, e.g., in
As shown most clearly in
The brake assembly also comprises brake rotor 59, brake stator 69, pin 67 and brake puck 60. Puck 60 is located in a cam pocket 68c formed in vertical portion 68b of brake arm 68. Pin 67 and stator 69 are preferably mounted in as-cast pocket 1c formed in housing member 1, as shown most clearly in
When brake arm 68 is rotated, puck 60 is moved to the left in
It is generally known to have a filter housing secured to the bottom of a center section adjacent to the check valves to prevent contaminants from the common sump from entering the closed hydraulic circuit. One embodiment of the present invention provides for separate snap-on filters for each check valve. For example, a snap-on filter for connection to center section 3 is depicted in
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any equivalent thereof. For example, the brake, swash plate, filter, gear train arrangement, bypass mechanism and other features disclosed herein may be used in conjunction with the other features shown herein or on their own in connection with another hydraulic apparatus design. Additional features and benefits of this invention are depicted in the figures.
Claims
1. A hydraulic drive apparatus, comprising:
- a hydraulic motor cylinder block disposed on a motor running surface in a sump;
- a motor shaft driven by the motor cylinder block; and
- means for moving the motor shaft along its axis of rotation to cause the motor shaft to engage a portion of the motor cylinder block to force the motor cylinder block to lift off the motor running surface.
2. The hydraulic drive apparatus of claim 1, further comprising biasing means to bias the motor shaft to a position where it is disengaged from the portion of the motor cylinder block.
3. The hydraulic drive apparatus of claim 2, wherein the biasing means comprises a spring engaged to one end of the motor shaft and to an internal surface of a housing.
4. The hydraulic drive apparatus of claim 1, further comprising a center section mounted in the sump, wherein the motor running surface is on the center section, and the center section further comprises a pump running surface on which a hydraulic pump cylinder block is disposed.
5. The hydraulic drive apparatus of claim 1, wherein the means for moving the motor shaft comprises a rod having a first end engaged to the motor shaft proximate to one end of the motor shaft and a control arm engaged to a second end of the rod.
6. A hydraulic apparatus for driving at least one rotatable axle, the hydraulic apparatus comprising:
- a running surface;
- a rotatable hydraulic element disposed on the running surface; and
- a drive train for transmitting force to the axle, the drive train comprising a shaft having a longitudinal axis and engaged to the rotatable hydraulic element, the shaft having a first position that permits the rotatable hydraulic element to remain in contact with the running surface and a second position where the shaft moves the rotatable hydraulic element away from the running surface.
7. The hydraulic apparatus of claim 6, wherein the shaft is biased to the first position.
8. The hydraulic apparatus of claim 7, wherein the shaft is biased by a spring acting on the shaft.
9. The hydraulic apparatus of claim 6, further comprising an actuator that engages the shaft to move the shaft between the first and second positions.
10. The hydraulic apparatus of claim 9, further comprising a groove formed in the actuator and a shoulder formed on the shaft that engages the groove.
11. The hydraulic apparatus of claim 10, wherein the actuator comprises a rod extending in a direction perpendicular to the longitudinal axis of the shaft.
12. The hydraulic apparatus of claim 11, wherein the actuator is biased to place the shaft in the first position.
13. The hydraulic apparatus of claim 6, further comprising a center section on which the running surface is formed, wherein the rotatable hydraulic element comprises a motor cylinder block, and the shaft comprises a motor shaft engaged to and driven by the motor cylinder block.
14. A hydraulic apparatus, comprising:
- a hydraulic mounting component comprising porting and a running surface;
- a rotatable cylinder block positioned on the running surface and in hydraulic communication with the porting;
- a sump adjacent to at least a portion of the hydraulic mounting component and generally surrounding the exposed portions of the rotatable cylinder block; and
- a shaft engaged to and rotating with the rotatable cylinder block, the shaft having a first position that permits the rotatable cylinder block to generate pressure in the porting and a second position where the shaft positions the rotatable cylinder block away from the running surface to prevent pressure from building in the porting.
15. The hydraulic apparatus of claim 14, wherein the hydraulic mounting component comprises a center section.
16. The hydraulic apparatus of claim 15, wherein the rotatable cylinder block comprises a hydraulic motor, the center section further comprising a pump running surface on which a hydraulic pump is positioned.
17. The hydraulic apparatus of claim 16, wherein the shaft comprises a motor shaft engaged to and driven by the hydraulic motor.
18. A hydraulic drive apparatus, comprising:
- a housing forming a sump;
- a center section mounted in the sump and having hydraulic porting formed therein;
- a pump running surface and a motor running surface on the center section;
- a hydraulic pump cylinder block disposed on the pump running surface and in fluid communication with the hydraulic porting;
- a hydraulic motor cylinder block disposed on the motor running surface and in fluid communication with the pump cylinder block through the hydraulic porting;
- a motor shaft splined to the motor cylinder block at a first location, whereby the motor cylinder block drives the motor shaft; and
- an arm engaged to the motor shaft for moving the motor shaft along its axis of rotation to cause the motor shaft to engage the motor cylinder block at a second location to force the motor cylinder block off the motor running surface.
19. The hydraulic drive apparatus of claim 18, wherein the motor shaft comprises a first end extending through the motor cylinder block and a second end, and the arm is engaged to the second end of the motor shaft.
20. The hydraulic drive apparatus of claim 19, wherein the first end and second end of the motor shaft are located on opposite sides of the center section.
21. The hydraulic drive apparatus of claim 18, wherein the motor shaft is engaged to and drives a first gear, and the first gear is located between the ends of the motor shaft.
22. The hydraulic drive apparatus of claim 1, further comprising a spring engaged to one end of the motor shaft to bias the motor shaft to a position where the motor shaft is disengaged from the motor cylinder block at the second location.
23. The hydraulic drive apparatus of claim 1, wherein the arm comprises a rod extending out of the housing in a direction perpendicular to the motor shaft.
24. The hydraulic drive apparatus of claim 23, further comprising a spring engaged to the arm to bias the motor shaft to a position where the motor shaft is disengaged from the motor cylinder block at the second location.
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Type: Grant
Filed: Feb 27, 2006
Date of Patent: Apr 22, 2008
Assignee: Hydro-Gear Limited Partnership (Sullivan, IL)
Inventors: Eric S. Phanco (Decatur, IL), Ryan S. Buescher (Neoga, IL)
Primary Examiner: Thomas E. Lazo
Attorney: Neal Gerber Eisenberg LLP
Application Number: 11/363,249
International Classification: B60K 17/10 (20060101); F16H 39/04 (20060101);